Assuming that everyone that survived was well outside of a city or suburban area, though, and stayed outside that fallout area for 10+ years, why would they be in such a hurry to move back? I'd think that once you set up a life somewhere and live there 10 years, you're unlikely to move right back into NYC or Chicago, for example.
And metal/raw materials would still exist, but pretty much anything else of value would have been consumed/destroyed as the cities of millions of people slowly self-destructed. And you'd likely still have those bands of cannibals and savages, and remnants of disease/filth would still be around.
Honestly, anyone that was anywhere NEAR those areas during the collapse would likely never want to return. You'd have lived to escape it, or seen refugees that had SEEN some things, or fought off the remaining savage survivors, etc. You'd put that city in your rearview mirror, associate it with some horrific things, and pretend it never existed. Just around NYC, for example, you've got probably 25-30 million people within say 50 miles or so. Even if a few thousand get out and survive, that's a LOT of death, and violently so.
And just to respond to a few of the comments, very familiar with the Dies the Fire series, big fan. Gets a little, uh, fantastic as it goes on, but the first few feel pretty 'real' as far as how things go down. Hoping there's eventually payoff with that series that both ties it to the Nantucket books, and resolves the overall cause of the Change. Great to resolve the overall plot in Montival, but I want the big answers, and think we're down to the last book or so here...